What has a more noticable effect on emmisions, high duration, high lift, or doesn't it make a differance? I'm debating buying either HKS 264's, or a higher lift cam(of similar duration) such as the Tomei procam or Piper road cams. It stands to reason that a cam of the same duration but w/ more lift would be dirtier, right? The reason I'm asking is that in PA we have to pay the air tax once a year, and I don't want to get into changing cams out every time I need a new sticker. Has anyone passed a Pa emmisions test w/ cams of any spec.? Thanks for the help!

 

High lift stock duration will give same emmisions as stock or darn near. Long duration cams have more overlap when the intake and exhaust valves are both open resulting in more emmisions.

Keith

 

Reducing overlap is your best bet to reduce emissions (within reason) you can run HKS 272 cams with -4/-1 but anything with increased overlap will increase emissions anyway.. The trick is to also have a very efficient ignition system so it burns the combustion gasses as completely as possible before its exhausted.. In other words, if your car misfires at idle, and has big cams, it'll likely have trouble passing idle emissions..

 

Thanks for the info guys, so the tomei or piper cams should be cleaner than the HKS 264's because they are closer to the stock duration?

 

I was over at Gude Performance last Friday and Mr. Gude was talking about wanting to prototype a 228 on my car. I would assume something like that would be pretty close to stock emissions wise... What's do you guys think? (don't mean to hi-jack thread)

 

No, you are using gross duration numbers as a means of comparison, which is inaccurate. In actuality, the effective duration of these cams is longer than the gross numbers would lead you to believe. To compare the effective duration of different cams, you need to know the duration at 1mm lift.